Griffin worked as an investigative reporter for CBS 2 News in Los Angeles for 10 years. He joined CNN in May 2004. In September 2005, Griffin covered the aftermath of Hurricane Katrina. Griffin's reports about the looting by some New Orleans police officers led to a police investigation. He also broke stories about nursing home deaths after Katrina.
Griffin won a business and financial reporting Emmy Award in 2005 for his reports on a fault in Ford vehicles which caused them to catch fire. He earned his second Emmy in 2006 for the CNN Presents documentary "How to Rob a Bank" and a third in 2007 for "Hidden Spending," an Anderson Cooper 360° segment about congressional spending.